1. Field of the Invention
The present invention relates to a print head. More particularly, the present invention relates to a piezoelectric ink-jet print head having selectively positioned actuators for precise operation.
2. Description of the Related Art
An ink-jet print head is a device which prints a picture with a predetermined color by ejecting a minute ink droplet onto a desired position of a printing medium. Such ink-jet print heads are divided according to the incorporated ink droplet ejection method into an electric-thermal transfer method, in which bubbles generated by heat cause the ink droplet to be ejected, and an electric-mechanical transfer method, in which a volume change due to deformation of piezoelectric elements is used to eject the ink droplet.
FIG. 1 is a partial cross-sectional view showing a general piezoelectric inkjet print head.
Referring to FIG. 1, the ink-jet print head includes a structure generally comprising a nozzle plate 300 provided with a nozzle 302, a reservoir plate 304 provided with a reservoir 306, a channel plate 308 provided with an ink inlet 310, a restrictor plate 312 provided with a restrictor 314, a chamber plate 316 provided with a pressure chamber 317, a vibrating plate 318, and an actuator 320, which are stacked as shown.
The actuator 320 includes a lower electrode 320a, a piezoelectric film 320b, and an upper electrode 320c, which are sequentially stacked. The pressure chamber 317 communicates with the nozzle 302 through an ink outlet 313 which passes through the restrictor plate 312, the channel plate 308, and the reservoir plate 304.
The ink supplied from an ink reservoir (not shown) is stored in the reservoir 306 and then flows into the pressure chamber 317 through the ink inlet 310. At this point, the restrictor 314, which is interposed between the ink inlet 310 and the pressure chamber 317, is employed to keep the inflow of the ink into the pressure chamber 317 at a constant speed.
When a voltage is applied between the upper electrode 320c and the lower electrode 320a of the actuator 320 disposed above the pressure chamber 317, the piezoelectric film 320b is energized and thus the vibrating plate 318 is deformed, thereby decreasing the volume of the pressure chamber 317. The pressure caused by such a decrease in the volume of the pressure chamber 317 results in the print head ejecting the ink from the pressure chamber 317 onto the printing medium through the ink outlet 313 and the nozzle 302.
FIG. 2 is a cross-sectional view showing a conventional piezoelectric ink-jet print head, taken along the line A-A of FIG. 1. Specifically, FIG. 2 shows a cross-section of a print head illustrating the width of pressure chamber 112. Hereinafter, the width direction of the pressure chamber 112 will be used as a short-axis direction thereof.
Referring to FIG. 2, the conventional ink-jet print head has a structure generally comprising a nozzle plate 100 provided with a nozzle 102, a reservoir plate 104, a channel plate 106, a restrictor plate 108, a chamber plate 110 provided with a pressure chamber 112, a vibrating plate 114, and an actuator 116, which are sequentially stacked. The actuator 116 includes a lower electrode 116a, a piezoelectric film 116b, and an upper electrode 116c, which are also sequentially stacked. The pressure chamber 112 communicates with the nozzle 102 through an ink outlet 109. As shown in FIG. 2, in the conventional ink-jet print head, the actuator 116 is disposed above the pressure chamber 112 and substantially covers the entire pressure chamber 112 in the width direction thereof. Therefore, any deformation of the actuator 116 is transferred entirely to the pressure chamber 112 via the vibrating plate 114. Therefore, too much pressure is often applied to the pressure chamber 112 when the actuator is energized, and thus, can limit the ability of the print head to decrease the size of the ink droplet, which is adjusted by the pressure.
Accordingly, a need exists for a print head in which an actuator and pressure chamber configuration is provided having greater control over a constant volume, such that the number of nozzles 102 per a unit area is not restricted.